title: Synergistic effect of various virulence factors leading to high toxicity of environmental V. cholerae non-O1/ non-O139 isolates lacking ctx gene : comparative study with clinical strains.
abstract: BACKGROUND
  Vibrio cholerae non-O1/ non-O139 serogroups have been reported to cause sporadic diarrhoea in humans. Cholera toxins have been mostly implicated for hypersecretion of ions and water into the small intestine. Though most of the V. cholerae non-O1/ non-O139 strains lack these cholera toxins, several other innate virulence factors contribute towards their pathogenicity. The environmental isolates may thus act as reservoirs for potential spreading of these virulence genes in the natural environment which may cause the emergence of epidemic-causing organisms.
  
  
  RESULTS
  The environmental isolates of vibrios were obtained from water samples, zooplanktons and phytoplanktons, from a village pond in Gandhinagar, Gujarat, India. They were confirmed as Vibrio cholerae non-O1/ non-O139 using standard biochemical and serotyping tests. PCR experiments revealed that the isolates lacked ctxA, ctxB, tcpA, zot and ace genes whereas other pathogenicity genes like toxR, rtxC, hlyA, hapA and prtV were detected in these isolates. Compared with epidemic strain V. cholerae O1 El Tor N16961, culture supernatants from most of these isolates caused higher cytotoxicity to HT29 cells and higher hemolytic, hemagglutinin and protease activities. In rabbit ileal loop assays, the environmental isolates showed only 2-4 folds lesser fluid accumulation in comparison to N16961 and a V. cholerae clinical isolate IDH02365 of 2009. Pulsed Field Gel electrophoresis and Random amplification of Polymorphic DNA indicated that these isolates showed considerable diversity and did not share the same clonal lineage even though they were derived from the same water source. All the isolates showed resistance to one or more antibiotics.
  
  
  CONCLUSIONS
  Though these environmental isolates lacked the cholera toxins, they seem to have adopted other survival strategies by optimally utilising a diverse array of several other toxins. The current findings indicate the possibility that these isolates could cause some gastroenteric inflammation when ingested and may serve as progenitors for overt disease-causing organisms.
authors.affiliation: Department of Human Health and Diseases, School of Biological Sciences and Biotechnology, Indian Institute of Advanced Research, Gandhinagar, Gujarat, India.
authors.forename: Neha
authors.initials: N
authors.lastname: Rajpara
authors.forename: Kittappa
authors.initials: K
authors.lastname: Vinothkumar
authors.forename: Priyabrata
authors.initials: P
authors.lastname: Mohanty
authors.forename: Arun Kumar
authors.initials: AK
authors.lastname: Singh
authors.forename: Rajesh
authors.initials: R
authors.lastname: Singh
authors.forename: Ritam
authors.initials: R
authors.lastname: Sinha
authors.forename: Dhrubajyoti
authors.initials: D
authors.lastname: Nag
authors.forename: Hemanta
authors.initials: H
authors.lastname: Koley
authors.forename: Ashima
authors.initials: A
authors.lastname: Kushwaha Bhardwaj
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D017931:DNA Primers / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004591:Electrophoresis, Polyacrylamide Gel; D005618:Fresh Water; D006801:Humans; D007194:India; D016133:Polymerase Chain Reaction; D011817:Rabbits; D019105:Random Amplified Polymorphic DNA Technique; D013045:Species Specificity; D014734:Vibrio cholerae / Q000235:genetics* / Q000472:pathogenicity*; D037521:Virulence Factors / Q000235:genetics* / Q000633:toxicity*; D014871:Water Microbiology
chemical_list: D017931:DNA Primers; D037521:Virulence Factors